This project is focused on understanding the physical and mechanistic properties of enzymes that underlie their exquisite function. In recent years, protein motions have been implicated as essential to achieve an extremely rapid catalysis of bond cleavage events. A spatial and temporal resolution of such protein motions is being pursued using enzyme prototypes that catalyze hydrogen and methyl transfer reactions. A description of the hierarchy and range of the requisite protein motions (covering time scales that can differ by ca. 1015 fold) will take place utilizing highly developed kinetic and biophysical probes. A second emerging area in biological catalysis concerns the post-translational modification of peptides that have been synthesized at the ribosome. A combination of structural and biochemical probes is addressing the enigmatic pathway that produces the bacterial cofactor and vitamin, pyrroloquinoline quinone. As the result of a number of recent breakthrough observations, it appears that resolution of this long-standing problem is now within reach.